1. Field of the Invention
This invention relates to an improvement of an apparatus, such as a camera, adapted to a film cartridge provided with an opening-and-closing cover.
2. Description of Related Art
In recent years, there is proposed a film cartridge provided with a light-lock door which serves as an openable and closable light-shielding cover arranged to shield a film egress/ingress slot from light. For example, a film cartridge disclosed in U.S. Pat. No. 5,347,334 is such a type of film cartridge. The film cartridge of this type necessitates a camera to perform opening-and-closing control over the light-lock door. For this control, the camera must be provided with a novel mechanism which is unnecessary for cameras adapted for use of a 135 film. An example of this mechanism has been proposed in Japanese Laid-Open Patent Application No. HEI 7-92534. According to this proposal, the light-lock door is driven to open and close through a spring balance between a plurality of springs.
However, since a driving force of the proposed mechanism for opening and closing the light-lock door is determined by the spring balance, the driving force is unstable. In order to reliably ensure the operation of the mechanism, an extremely strong spring force is necessary, thereby disadvantageously requiring a heavy operation. An attempt to lighten the heavy operation, on the other hand, makes a reliable operation impossible. Further, the incorporation of the proposed mechanism causes an increase in size of the camera. However, no art for preventing such a mechanism from increasing the size of cameras has been known.